1. Field of the Invention
The invention relates to a method and an apparatus of supplying slurry during chemical-mechanical polishing (CMP), and more particular, to an improved design of a slurry supply system by installing a bypass of a valve box therein.
2. Description of the Related Art
For a very large scale integration (VLSI) or even an ultra large scale integration (ULSI), chemical-mechanical polishing is the only technique that provides global planaration.
Referring to FIG. 1A and FIG. 1B, a conventional chemical-mechanical polisher comprises a polishing table 10, a polishing pad 12 and a polishing head on the polishing table 10. During polishing, the wafer 16 carried by the polishing head 14 is facing down. The polishing is performed with slurry supply 18 as shown in the figure.
In FIG. 2, a chemical-mechanical polishing slurry supply system designed by MEGA is shown. Being blended by reacting chamber 206 and distributed by distributing chamber 205, the slurry is flowing through a thicker pipe 207 to valve boxes 203 and 204 connected in serial. By applying Bernoulli's law, the slurry is then flowing through a thinner pipe 208 to various polisher 201 and 202. In a conventional slurry supply system, five valve boxes are disposed in serial, that is, a conventional slurry supply system can supply five polisher for polishing at a time by disposing valve boxes in serial.
In FIG. 2, valve boxes 203 and 204 are disposed on the bypass of slurry. Since the slurry contains a large amount of particles, a dead leg is very likely to occur at the corner of the pipe to stock the pipe. In addition, in the above slurry supply system, the valve boxes are connected in serial. Once one of them is out of order or stocked, the rest of the valve boxes are affected, the whole system is down, and the polishing has to be broken off.